JMH is the JVM Microbenchmark Harness developed as part of the OpenJDK. There are lots of nice resources about JMH out there. This guide, written back in 2014, still provides some valuable information for someone who wants to start with JMH. Then, there are the samples, which are a must-read and part of the source tree of JMH.
One thing that I couldn’t find and that could be practical was a cheatsheet, so I put this one together. It’s largely based on the JavaDocs of the annotations, but I personally find it useful to have all the info on a single page.